1. Field of the Invention
This invention relates to a device for controlling the safety of an active seismic response and wind control system installed in a structure in order to reduce the vibration of the structure caused by an external force such as earthquake and wind.
2. Description of the Prior Art
This applicant has disclosed in Japanese Patent Laid-open Nos. Sho 62-268478 and Sho 63-78974 an active seismic response and wind control system, which consists of an additional mass and an actuator and is provided on the top or the like of a structure, and in which the operation of the actuator is controlled when a structure is subjected to an external force such as earthquake and wind, whereby the reaction given to the weight as an additional mass applies a vibration control force to the structure body.
FIG. 6 shows an outline of the active seismic response and wind control system as noted above, in which a weight 12 used as an additional mass is provided on the top of a structure 1, for example, in such manner that the weight 12 is substantially separated from the structure 1, and an actuator 3 is interposed between the weight 12 and a portion of the structure 1. When the structure 1 vibrates under the action of earthquake, wind or the like, a sensor 13a provided on the structure 1 senses the vibration of the structure 1 to send a signal to a control circuit. The control circuit sends an output signal corresponding to the vibration of the structure 1 to the actuator 3 and controls the actuator 3. Further, a sensor 13b is provided on the side of the actuator 3 to feed back the motion of the actuator 3, whereby the actuator 3 is accurately controlled.
Now, though the seismic response and wind control system has no difficulty under the normal operation, it should be contemplated that any abnormalities in the drive or control of the system take place by various causes such as a reduction or excess of hydraulic pressure, a shortage of oil amount on a hydraulic pressure source, an overload (load and stroke) on the actuator, or unexpected causes in devices utilizing the hydraulic pressure, for example.
Particularly, since the active seismic response and wind control system makes use of external energy, it is liable to instead apply the vibration to the structure due to the inverse action of the external energy.